Control system for pulverized fuel



Nov. 22, 1938. E. v. FRANCIS 2,137,754

CONTROL SYSTEM FOR PULVERIZED FUEL BUHNERS Filed April '26, 1955 4 sheets-sheet 1 //v VENTOF? far/e l/. 56/? 0'5,

5 Y. 0&1; m WW ATT'Y.

Nov. 22, 1938. E. v. FRANCIS CONTROL SYSTEM FOR PULVERIZED FUEL BURNERS 4 Sheets-Sheet 2 Filed April 26, 1935 ATT'Y Nov. 22, 1938. E. v. FRANCIS CONTROL SYSTEM FOR PULVERIZED FUEL BURNERS 4 Sheets-Sheet 5 Filed April 26, 1955 LUP ATT'Y N MMN E. v. FRANCIS 2,137,754 CONTROL SYSTEM FOR PULVERIZED FUEL BUHNERS Filed April 26, 1935 4 Sheets-Sheet 4 lllllll Ear/e l/ fianC/s) E. BY I (7 0 aux/Q m M TT'y Patented Nov. 22, 1938 UNITED STATES CONTROL SYSTEM FOR PULVERIZED FUEL I BURNERS Earle V. Francis, Columbus, Ohio, assignor to The Jeffrey Manufacturing Company, a corporation of Ohio Application April 26, 1935, Serial No. 18,336 4 Claims. (01.110-28) The invention relates to an electrical control system particularly adapted for pulverized coal burners.

An object of the invention is to provide a completely automatic control system for a pulverized coal burner, particularly of the type designed for domestic use, which is very efficient and economical in operation yet is operative to insure the proper control of the burner.

A specific object of the invention is toprovide an improved control system for a pulverized coal burner having a preliminary combustion chamber, which system is fully automatic and which employs a combined gas and electric ignition means, in which the operation of the electric ignition means is discontinued after a short period of fuel combustion, while the gas ignition means is operative for a somewhat longer period and until a pulverized coal combustion supporting temperature is reached within the preliminary combustion chamber, after which saidgas ignition means is also renderedinoperative;

Another specific: object of the invention is to provide an improved control system for a pulverized fuel burner having a preliminary combustion chamber, which system is fully automatic and which employs a combined gas and electric ignition means, which electric ignition means is energized prior to the energization of the gas ignition means and which electric ignition means is cut off after a short period of fuel combustion while the gas ignition means is operative for a somewhat longer period and until a pulverized coal combustion supporting temperature is reached within the preliminary combustion chamher, after which said gas ignition. means'is also rendered inoperative.

Other objects o-fthe invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

Referring to the accompanying drawings: Fig. 1 is an elevational View of an automatic thermostatically controlled domestic heating system embodying the improvements of the present invention, with the furnace shown in section;

Fig. 2 is a circuit diagram of one circuit of my invention; 9

Fig. 3 is a circuit diagram of another circuit of my invention; I Fig. 4 is a circuit diagram of a third circuit of myinvention;v g Fig. 5 is a front elevational view of the com bined stack controlled switches and the relays 55 adapted to be used with the circuit of. Fig.2 with the stack controlled switches in the shut-down position; v

Fig. 6 is a detailed view of the switches of Fig. 5, when the system has just started operation;

Fig. 'I is a detailed view similar to Fig. 5, when 5 the system is in full operation;

Fig. 8 is a sectional view of the thermostatically controlled. stack switches seen in Figs. 5, 6 and *7;

Fig. 9 is a front elevational view of the control mechanism, except'for the stackswitches, em- 10 ployed with the circuits of Figs. 3 and 4, shown in its normal condition when the system is shut down;

Fig. 10 is a. view of the mechanism of Fig. 9, with certain parts removed for clarity, during the 15 starting of the combustion device;

Fig. 11 is a view of the mechanism of Fig. 9, with certain parts removed for clarity, during-the running period; and

Fig-12 is a view of the mechanism of Fig. 9, 20 with numerous parts removed for clarity, when there is a current interruption during the ignition period just before the fuel motor is turned on.

Referring particularly to" Fig. 1, there is illustrated an installation comprising a domestic heat- =25 ing unit which is automatically thermostatically controlled by the control system comprising my invention and in which pulverized fuel is employed. The installation comprises a furnace A, which is illustrated as of the hot air type, al- 30 though it may be of the hot water or steam type, including a fire box or main combustion chamber B, within which is positioned a preliminary combustion chamber C. The preliminary combustion chamber C is an important element of my inven- 35 tion for it has been found after exhaustivetests that a preliminary combustion chamber is necessary for the proper combustion of pulverized fuel, such as pulverized coal. This is due to the fact that the pulverized fuel is not subject to any '40 extensive pre-heating and must be completely ignited within the fire box or main combustion chamber B. The combustion chamber temperature necessary for proper combustion of powdered or pulverized coal is approximately 2000 to 2500 degrees Fahrenheit which is, in general, more than twice the combustion chamber. temperature necessary for proper combustion of fuel oil and is many times the combustion chamber temperature necessary for proper combustion of gas. For eX- ample, gas will burnin an. open room at room temperature but this is not possiblewwith most fuel oils and is entirely impossible with pulverized coal. For fuel oils,:the combustion space temperature mustbe higherthan for gas and for of standing the above pulverized fuel it must be still higher. The latter is higher than ordinary domestic furnaces, made of iron, can stand.

The preliminary combustion chamber C is made of fire brick or other refractory material and is designed so as to be heated to a very high temperature in a relatively short period of time, whereby it will be effective to maintain'combust'ion .of the pulverized coal. That is, the preliminary cornbustion chamber C is heated by the combined gas and pulverized coal, the former being electrically ignited, during initial combustion and reaches a pulverized coal combustion supporting temperature by forming a hot spot on the interior thereof against which the pulverizedfuel is *fed. This hot spot is preferably not concentrated, but spreads over a substantial area of the interior of said combustion chamber to prevent rapid deterioration of said preliminary combustion chamber. combustion chamber C, the-gasneeds to be em ployed only for a relatively short period and until the mentioned pulverized coal combustion supporting temperature is reached. In practice this may vary from 3 to 12 minutes. The period during which the electrical ignition means is energized may .be appreciably less as it need only ignite the gas. After the preliminarycombustion chamber C has reached the pulverized coal combustion supporting temperature, the gas may be turned off and the preliminary combustion chamber C will be effective to ignite the pulverized fuel delivered thereto and will maintain combustion thereof. This preliminary combustion chamber C also performs the additional function :of protecting the walls of the fire box or main combustion chamber .3, which are usually of iron and are incapable mentionedhigh temperatures. Said preliminary combustion chamber C is preferably open at the. bottom forit has been found that if the bottom of said chamber C is closed an accumulation of spongy ash will result and clog said preliminary combustion chamber within a short time, thereby rendering the furnace inoperative.

The form of said chamber may be varied somewhat from that illustrated in the drawings and may take the form illustrated :in any .of the different species disclosed in my application .Serial No. 716,119 filed in the U. S. Patent Office on March .17, 1934, of which theinstant application .constitutes a continuation in part.

In the operation of thesystem, :the pulverized coal is fed through the open bottom of thepreliminary combustion chamber C through the nozzle D having a lower pulverized coal conduit and an upper ignition conduit and which may take the form of the nozzles illustrated in any of the figures of my above mentioned application. The pulverized coal is stored in thebin Eand fed' through the conduit F to the nozzle D'by means of a feeding mechanismf driven by an electric motor H. The detailed structure of the feeding mechanism G preferably takes the form disclosed more in detail in myapplicationSerial No. 652,975

filed in the U. S. Patent Office on-January 23, 1933.

An ignition means, including a transformer 1 and an igniter J, is provided which is of the combined gas and electric type. That is, the igniter J comprises a gas jet nozzle '20 which is supplied with gas from the usual commercial source and is controlled by a gas valve 2|. As the .gas is .admitted from the gas jet nozzle into the upper ignition conduit of burner nozzle D, it is ignited by either a spark or. incandescent type electric Due to the presence of this preliminary igniter 22 which may take the form of any of the igniters disclosed more in detail in my above mentioned application, Serial No. 716,119.

The control of the combustion within the furnace A is entirely automatic and responds to the temperature of a control thermostat 23, such as a room thermostat. Various control relays and switches are provided, as will be hereinafter described more in detail, some of which are responsive to the temperature in the stack K associated with the furnace A and, as illustrated in Fig. 1, these control devices are mounted within a control box L. A line switch M is provided for controlling the energization or de-energization of the entire system.

As will be hereinafter pointed out more specifically in considering the several control circuits, the room thermostat 23 will be effective to start up the feed mechanism G to feed pulverized coal to the furnace A whenever the room temperature reaches a pre-determined low value. The control System will automatically operate to turn on the igniting gas and the electrical ignition means to ignite the pulverized coal during a preliminary period. After a short period of combustion, the electrical ignition means will be turned off as it would be uneconomical to maintain it energized for a long period. The igniting gas, however, will be maintained for a longer period and until the preliminary combustion chamber C has reached such a temperature that the incoming pulverized fuel will be ignited thereby without the .aid of the gas. When this temperature of the preliminary combustion chamber is reached, the igniting gas will also be turned off and the control of the feed mechanism G will be directly under the supervision of the room thermostat 23 and will be rendered operative until the room, in which said room thermostat 23 is located, has reached a predetermined temperature. Auto- .matic means is also provided so that the system would be rendered entirely inoperative and will require a manual re-setting should combustion not be properly established.

Attention is directed to Figs. 2, 5, 6, 7 and 8, the first of which is a circuit diagram representing one control circuit comprising my invention and the last four of which illustrate the structure of the mercury switches and the operating means therefor. The condition of the circuit, as illustrated in Fig. 2, is representative of the situation a short interval after the room thermostat has been closed in response to a 'low room temperature. Upon the closing of the contacts of said mercury switch 23, relay 24 will be energized through a circuit from the left hand terminal of the secondary 25 of transformer T through said relay 24, the contacts of mercury switch 23, the heating resistor 26, the normally closed contacts of slow mercury switch 21 and the right hand terminal of the secondary 25 of said transformer T. The primary winding 28 of said transformer T is normally energized directly from the line conductors 29 and 30, which are connected to the usual source of alternating current through the switch ,M of Fig. 1. It may be noted that a safety switch 3|, comprising a mercury tube, is connected in the line conductor 30 and it is necessary that the contacts of this switch 3| be in a closed position in order that the control system may be operative.

When the above described circuit, including relay 24, is closed, thenormally open contacts of mercury switch 32 are closed and a circuit is provided from the line conductor 29 through the motor H of the feed mechanism G to the line 30 by way of safety switch 3|. Thus the energize.- tion of relay 24 is effective to start the operation of feed motor H and is effective to start the delivery of powdered coal from the storage bin E to the furnace A. The switch 32 also causes energization of the gas control valve 2| and the electric spark ignition means 3 simultaneous with the energization. of motor I-I. Said gas control valve 2| is controlled through the solenoid 34, the terminals of which are connected between the lines 29 and 30 throu'ghthe normally closed contacts of mercury switch and/or parallel mercury switch 46, mercury switch 32 and safety switch 3|. The spark ignition means 33 is energized by virtue of the fact that the primary of transformer T is connected between the line conductors 29 and 39 through the normally closed contacts of fast mercury switch 36 and through the contacts of mercury switch 32 and safety switch 3| over an obvious circuit. The spark ignition means 33 is connected to the terminals of the secondary winding 31 of transformer T. s i

It is thus evident that the closing of mercury switch 32 is effective to cause a simultaneous operation of the pulverized fuel feed mechanism G, the opening of the gas valve 2| and the energization of the spark ignition means 33. Under these conditions, pulverized coal will be fed to the preliminary combustion chamber C through the nozzle D which will be ignited by a flame of burning gas which issues from the top conduit of said burner nozzle D, which flaming gas is ignited by the electrical spark ignition means 33.

Combustion is thus initiated in the furnace A.

In response to the combustion in the furnace A, the thermostatic stack controlled mechanism illustrated in detail in Fig. 8 will become operative whereby the bi-metallic helix 33 will start to turn the shaft 39. Upon said shaft 39 there is impositively mounted a pair of levers 40 and 4|. There is sufficient frictional engagement between said shaft 39 and the levers 4|] and 4|, which is provided by appropriate springs, so that the levers 4D and 4| tend to rotate with said shaft 39. The rotary movement of the lever 46 is restrictedby a pair of spaced pins 42 and the rotary movement of the lever 4| is restricted by a pair of adjustable spaced pins 43.

The normal non-operating position of the levers 40 and 4| is illustrated in Fig. 5 in which lever 46 is at its extreme right hand position and adjacent the right hand pin 43. As the shaft 39 rotates, under the influence of heat, in a counter-clockwise direction, the lever 4|) moves from the right hand pin 42 to the left hand pin 42 in a relatively short period of time or in response to a relatively low combustion tempera ture. Said arm 40 carries the normally closed mercury switch 36 and the normally open mercury switch 44. Thus, when said lever 40 moves from the right hand pin 42 to the left hand pin 42 in response to initial combustion in the furnace A, it is effective to break the contacts of mercury switch 36 which cuts out the electrical ignition means 33. It also closes the contacts of mercury switch 44. The function of the mercury switch 44 is to insert a resistor 45 in a series circuit including the secondary 23 of transformer T, relay 24, the contacts of switch 23 and safety heating resistor 26, whereby the relay 24 will be maintained energized after mercury switch 21 is open in response to a prolonged or higher combustion temperature and will prevent the energization of a bi-metallic safety device associated with the safety heating resistor 26 for operating the safety switch 3|. This will be explained more in detail hereinafter.

After a higher combustion temperature is reached or the combustion has been prolonged for a more extended period within which the preliminary combustion chamber C reaches a pulverized coal combustion supporting temperature, shaft 39 will be operative to move the lever 4| to the left-hand pin 43 and, just before this position is reached, the contacts of the normally closed mercury switches 21 and 35 will be opened. Switch 21 may be adjusted so as to open ahead of switch 35. The opening of contacts of mercury switch 35 will open onecircuit to the solenoid 34 of the gas valve 2|. However, this solenoid will still be energized by virtue of a normally closed mercury switch 46 which is associated with a very slow stack controlled mechanism 41. That is, the stack controlled mechanism 47 is effective to open the contacts of mercury switch 46 only after a heating period which is in excess of that required to open switches 21 and 35. This stack controlled mechanism may be of the general type illustrated in Fig. 8 except that, of course, there will be only one lever and one mercury switch associated therewith which will be adjusted for very slow operation, or it may take the form of any other well-known temperature responsive control mechanism. The opening of the contacts of the mercury switch 21 is effective to reduce the current in the previously closed circuit, including secondary 25, the relay 24, contacts of switch 23 and the safety heat resistor 26 and to insert effectively in said series circuit the resistor 45 through the contacts of switch 44. This so reduces the current in the resistor 26 that the bi metallic safety operating device associated therewith will not be operated.

After a prolonged combustion period, which is determined by the adjustment of the stack controlled mechanism 4'|, the solenoid 34 will be de-energized and the gas shut off. This repre sents the normal running condition in which the supplying of pulverized coal to the furnace A is directly controlled by the room thermostat 23.

After the room has reached a predetermined temperature, the contacts of mercury switch 23 will be opened whereupon relay 24 will be deenergized, thus opening the circuit to motor H of the feed mechanism G and discontinuing the supplying of pulverized fuel to the furnace. All of the stack controlled or heat responsive mercury switches 21, 35, 33, 44 and 43 thus begin to return to their normal positions as the temperature in the furnace A decreases. Upon the temperature in the room again reaching the minimum temperature to which it is adjusted, the above mentioned cycle of operation will be repeated.

In order to provide a safety device whereby the system will be rendered entirely inoperative, if proper combustion does not take place in the furnace A within a pre-determined time, automatic means are provided for preventing operation of the system under the mentioned conditions. Assuming, for example, that after relay 24 is energized and contacts of switch 32 are closed, combustion does not take place, or does not take place at a sufficiently rapid rate to en ergize the helix 38 properly, a current will flow through the series circuit comprising transformer secondary 25, relay 24, contacts of switch 23, safety heating resistor 26 and the contacts of switch 21.. Associated with the safety heating resistor 26 is. a bi-metallic strip 48. With this resistor 26 heated by the normal current flowing through the above. mentioned circuit, it will be effective to deflect the bi-metallic strip 48 so that after a pre-determined period of time said strip 48 will release a latch 49 (Fig. which, when released, will allow the mercury switch 3| to tilt under the influence of gravity and open the contacts thereof. When the contacts of said safety switch 3| are opened, the entire system is disabled and, it is necessary to re-set. manually the control mechanism to close the contacts of said safety switch 3| by the operation of a re-set knob 50. It is to be noted that in the ordinary operation of the system, the contacts of switch 44- are closed after which the. contacts of switch 2! are opened before strip 46 is deflected sufficiently to release latch 49, in which case the current flowing through the mentioned circuit, now including resistor 26, will be reduced to an amount insufficient to operate the safety switch 3| even though it flows indefinitely.

Attention is directed to the fact that the two switches 35 and 46 are effectively in parallel and thus, if either is closed, the gas valve 2| may be operated. This is to provide for the establishing of a circuit for the solenoid 34 of the gas valve 2| in case the system is shut down for a relatively short time during which the very slow switch 46 has not had sufficient time to close. This tends to prevent needless operations of the safety switch 3| which might otherwise take 1, place were switch 35 omitted.

It may be pointed out that in Fig. 2 the transformer T is shown as independent of the relay 24 but this construction is not necessary and they may be combined as a single unit. In Fig. 5 there is illustrated the combined transformer T and relay winding at T. The field core 5| operates as the field for the transformer and also as a core for the relay 24 which controls the switch 32. The primary of said combined relay and transformer T"is seen at 26.

Referring to Fig. 3 of the drawings, there is illustrated another circuit comprising my invention which has certain features of operation not present in the circuit of Fig. 2 and which is associated with an essentially different switch controlling mechanism which is illustrated in Figs. 9, 10, 11 and 12. One of the features of the invention of the control system of Fig. 3 lies in the fact that an incandescent type of electrical ignition means is provided and this electrical ignition means is heated for a pre-determined period so as to reach incandescence before the gas valve is opened and the motor H of the feed mechanism G is operated. This period may be termed the pre-ignition period.

The condition of the system as illustrated in Fig. 3 is just after the room temperature responsive switch 66 is closed. The control system of said Fig. 3 includes a pair of line conductors 60 and GI which are connected to the usual source of commercial alternating current-as, for example, through the switch M of the type illustrated in Fig. 1. A mercury safety switch 62 is in the line 6| and may be operated from any safety device such as an over-pressure gauge associated with a steam boiler or an over-temperature thermostat associated with an air or hot water furnace. The transformer 63 has its primary 64 connected directly across the line conductors 66 and 6|. The secondary 65 of the transformer 63 has its terminals directly connected to the terminals of the room temperature responsive mercury switch 66. It is thus evident that upon closing of the contacts of the room temperature responsive switch 66, the secondary 65 of the transformer 63 will be energized. Energization of said secondary 65 is effective to close the normally open mercury switch 61 in the line conductor 6|. A movable solenoid may be associated with said secondary 65 for operating said mercury switch 6'! or said secondary 65 may be of the floating coil type and be effective to close the contacts of said switch 61 when energized. Upon the closing of contacts of mercury switch 61, it is evident that line voltage will be applied to the lines 60 and BI and any devices which are directly connected between these lines will be energized. The only device, excepting winding 64, which is directly connected across lines 60 and 6| when the terminals of switch 61 are closed, is the floating primary winding 68 of the constant current transformer 65. The circuit to said primary winding 68 is an obvious one and includes the normally closed contacts of mercury switch 10.

Referring more particularly to Figs. 9, 10 and 11, there is illustrated the structural details of the constant current transformer 69 and its association with other control elements of the system. Said constant current transformer 69 comprises a shell type core 1| having a central leg 12 upon which is mounted the floating primary winding 68 and a. stationary secondary 13. When the floating primary coil 68 is energized, as aforesaid, it will be lifted upon the leg 12 due to magnetic repulsion between the primary 68 and the secondary 13. As the transformer 69 is of the constant current type, a constant flow of current will be induced in the closed secondary circuit thereof (Fig. 3) which includes stationary winding 13, incandescent ignition means 14 and bimetallic thermal element 15. This flow of constant current in said secondary circuit will heat the incandescent ignition means 74 to a proper temperature within a pre-determined time which will be constant regardless of any voltage fluctuations due to the constant current transformer and will cause the bi-metallic thermal element 15, by reason of the heating thereof by the current flowing therethrough, to deflect to the right as viewed in Figs. 9, 10, 11 and 12.

As the thermal element 75 is deflected, it is effective to close the normally open contacts of gas switch 16, which is of the mercury type, and to close the normally open contacts of motor switch 11, which is also of the mercury type. While both the mercury switches I6 and T1 are operated by the bi-metallic thermal element 75, they are so adjusted that the contacts of switch 16 are closed a short interval of time prior to the closing of the contacts of switch 11. The closing of the gas switch 16 is effective to close a circuit to the operating solenoid I8 of the gas valve 2| a through the normally closed contacts of switch 19 or the normally closed contacts of switch 80, which switches 19 and 80 are connected in parallel. Thus the closing of switch 16 opens the gas valve 2|a and supplies gas to the furnace A which will be ignited by the ignition means 14. After a very short interval of time, the closing of motor switch 11 will close the circuit to the motor H and start the feeding of the pulverized coal by the feed mechanism G to the furnace A. Combustion is thus initiated.

Referring particularly to Figs. 9, 10, 11 and 12, attention is directed to the structural details of the control mechanism and its operation in performing the above described functions. The

cuit, including the secondary 13 of transformer 69, the ignition means 14 and said thermal'element 15, the floating primary winding 68 rises, as illustrated in Fig. 10, and the element 15 starts. deflecting to the right. The floating primary winding 68 carries a pair of lateral'projections, one of which is seen at 82 in Figs. 10 and 11, which projections are adapted to strike against a pair of pivoted levers, one of which is seen at 83 in Figs. 10 and 11, when said floating coil is in the lowered position and is de-energized. The rising of the floating winding 68 in response to its energization lifts the projections 82 from the levers 83 and allows the bracket 84 to move downwardly. Said bracket 84 is pivoted at each side, one of the pivots being seen at 85 in Figs. 10 and 11. The bracket 84 is connected by a shaft 86 to a lever 81 which is pivoted about a pivot 88. The downward movement of the bracket 84 is positively transferred to the lever 81 but the-upward movement of said bracket 84 is transferred to the lever 81 through a compression spring 89. Also attached to the lever 81 is a retarding dash pot90 which dampens the action of the lever 81.

The gas switch 16 and the motor switch 11 are carried on a carrier plate 9| which is pivoted at 92 and is normally biased by gravity to move in. a clockwise direction. I Said carrier plate 9| is provided with an arm 93 with which cooperates a pin 94 carried by the lever 81. When the floating primary winding 68 is in its lowered position, the lever 81 is rotated clockwise and the pin 94 is effective to rotate the carrier plate 9| in a counter-clockwise direction and to maintain the contacts of switches 16 and 11 in an open position. This. of course, is their normal nonoperating position. When the floating primary winding 68 is in its raised position. the lever 81 will be pivoted to lift the pin 94 from the arm 93, thereby allowing the carrier plate 9| to pivot in a clockwise direction and close the contacts of mercury switches 16 and '11. However, this rotation of the carrier plate 9| is also controlled by the projecting finger 95 carried by the plate 8| which cooperates with arm 93 so that carrier plate 9| cannotrotate to close the contacts of mercury switches 16 and 11 until the plate 8| is rotated in a clockwise direction about its pivot 96 under the influence of the thermal element 15. The thermal element 15, upon being heated and deflecting to the right at a uniform rate, rotates theplate 8| about said pivot 96 through the intermediary of the pivoted lever 91. This motion is positive. as the thermal element 15 defiects to the right but is impositive through a lost motion tension spring connecting means 98 when the thermal element 15 restores to normal. 7 The effective length of the lever!" may be adjusted by an adjusting mechanism 99 whereby the time intervalsbetween the first energization of the thermal element 15 and the closing of the mercury switches 16 and TI may be adjusted. This provides for a variable determination of the period during which the ignition means 14 is energized prior to the time that the gas is turned on and the period during which the gas is turned on prior to the time the motor H is operated.

After the thermal element 15 has been deflected a pre-determined. amount and the plate 8| thereby pivoted in a clockwise direction a pre-determined amount, the finger 95 will allow pivotal movement of the carrier plate 9| to a position first to close the gas switch 16 and after a short interval to aclose the motor switch 11. When these events have taken place, the mechanism will be in full operation with the ignition means 14 energized, the gas valve 2|a open and gas being delivered to the furnace, and the motor H operating and delivering powdered coal to theZfurnaLceZ-Z Combustion of the powdered coal 'wi'l-l thereby be' initiated, assuming that everything operates properly.

When the system of Fig. 3 and the controlmechanism of Figs. 9, 10, 11 and 12 is employed, said control mechanism will preferably not be associated with the stack K as is generally illus-' trated for the control box L in Fig. l, but will be positioned at a remote point for example, on an appropriate panel on a wall in the building, or it may be positioned adjacent the transformer T. However, there'will be associated with the stack K a combustion'responsive stack switch carrying two mercury switches, one of which operates in a short interval of time and the other of which operates in a relatively long interval of time; These stack switches may be operated by a mechanism similarto that illustrated in Fig. 8 except that only two stitches will be employed instead of the four illustrated. One of the switches would be a fast switch and might correspond to theswitch 36 of Fig. 8 and the other switch would be a slow-switch and might correspond to:the switch 35.

With conditions as above described and with combustion initiated in the furnace A, the thermostatic stack control mechanism I88 (Fig. 3) will be operated and will first close the normally open contacts of the fast mercury switch NH. The closing of the contacts for this switch |8| will energize the relay coil I82 which will operate to openthe normally closed contacts of mercury switches 18 and 19. The opening of the contacts of mercury switch 18 will de-energize the circuit to the floating primary winding 68. The opening of the contacts of the mercury switch 19 will beuwithout effect at this time due to the closed condition of the normally closed contactsof mercury switch.80, which is connected in parallel therewith.

Asa result of the de-energization of the fiqating winding 68, this winding will drop to its lowered position, the circuit, including the stationary secondary l3, ignition means I4 and thermal element 15, will be de-energized and the thermal elementp'lS will -startto cool and to assume a normal position. Apre-determined time interval after the mercury switch It! closesitscontacts and within a time limit sufiicient to heat the preliminary combustion chamber to a pulverized coal combustion supporting temperature, which will ordinarily be from 2 to minutes, the contacts of mercury switch 89 will be open and the. gas. ;valve solenoid l8 de-energized,

thereby closing the. gasyalve Zla and shutting off the supply of gas.

This presents the normal running condition of the system in which the motor H is operating the feed mechanism G to supply fuel-to the furnace A under the direct control of the room thermostat 86 and when the roomtemperature becomes sufliciently high to open the contacts of "the switch .and thereby open the circuit of switch Blythe entire mechanism will .be disabled, the .motor H shut down and the mechanism will :restoreto its normal non-operating condition.

Referring particularly to Figs. 9., 10, '11 and 12, attention is now directed to the operation of the control mechanism in response to combustion conditions which are effective .to close mercury switches -I.0I and I30, as above described. The condition .of the control mechanism before the stack controlled mechanism was effective to close the contacts of switches 10] and 80, is illustrated in Fig. 10. When'mercury switch IOI closes and relay coil I02 is energized, the armature I 03 of .the relay associated with said cell I02, is attracted and is' 'eifective .to move the lever I04, best seen in Figs. 10 and 11, about its pivot I05. Lever I0! carries .an :.arm I06 which is moved in a counter-clockwise direction under the influence of armature I03, as illustrated in Fig. 11. Said arm Illicarries alatch "I 0''! which cooperates with a tongue I08 extending from the carrier plate '9I to latch said carrier plate 9| in a position where switches FIG and 1! will be closed'regardless of the position of lever 81 or plate 8|. In addition, the arm I06 has a notch I09, best seen in Fig. 10, which cooperates with lever 81 to maintain said lever 'in a position illustrated in 1i withmit regard to the position, of the floating primary'winding 68. The armature I03, through its back lever I03, (Fig. 11) cooperates with a plate I=I0 which is loosely pivoted on a pivot III to rotate said plate about said pivot in a counter-clockwise direction. Said plate 'I I0 carries a pin II2 'adapted'to move the plate I I3 in a counter-clockwise direction 'upon striking an arm II! thereof. The plate H3 is also pivoted on pivot "Mil. .Plate Ii-3 carries the two mercury switches I0 and :19. Thusthe energization of the coil I02 is effective to pivot the plate H3 and to move the switches I0 and I9 from a closed position to an open position.

This results in :the turrrn'ng 'oif of the ignition means I4 and the locking of the motor switch 11 and the gas switch 16 in a closed position. The gas switch I6 is effective to keep the gas valve 2Ia open because both of the contacts of mercury switch are still closed. After the pre-determined combustion temperature is reached, as above mentioned, the contacts of mercury switch 80 are opened and the gas valve 2 Ia will close and-shut off the 'gas. This presents the normal running condition of the system and, as was above set forth, :is "illustrated in Fig. 11 of 'the drawings.

It may be pointed out that due to the de-energization of the floating primary winding 68 in response to the opening of the contacts of switch I0, said floating primary winding will drop and the thermal element I5 will restore to normal. The dropping of the floating primary winding 68, of course, again brings the lateral projections 82 into contact with the levers 83 and tends to rotate the lever 81 in a clockwise direction. This rotation of the lever 81 is prevented, however, as it is locked in position by the notch I09 of arm I 06, as was above described, and the floating primary Winding 68 cannot move to its lowermost position. Any tendency for the bracket 84 to pivot the lever 81 results in a compression of the spring '89. In addition, the plate BI is prevented from being pivoted in a counter-clockwise direction to its normal position under the influence of the thermal element I5 due to the contact beterm'ined room temperature, the motor .H'is shut down due to the opening of the contacts of switch 61 and combustion is terminated. 'This, of course, results in the thermal stack controlled mechanism returning the stack switches IIII and 80 to their normal positions, as illustrated in Fig. 3,

under which conditions the relay coil I02 is deenergized and the armature I03 is released. This releases the lever 81 and the carrier plate 9| whereupon the floating primary winding 68 is allowed to drop to its lowermost position. The

.carrier plate SI then pivots under the influence of pin 94 carried on lever "81 to open the contacts of gas switch "I6 and motor switch 11 and plate 01 rotates in a counter-clockwise direction to its normal non-operating position. Upon the room temperature dropping to a {ire-determined minimum, the above mentioned'cycle of operation :is repeated.

The control system of Fig. 3 and the control mechanism of Figs. 9, 10, '11 and 12 is provided with a number of safety features which will now be described. As was above mentioned, the stack controlled mechanism is so adjusted that in normal operation the ignition means "I4 will be disabled in response to a relatively short period of furnace combustion while the gas will be supplied to said furnace for a period suflicient to raise the temperature ofthe primary combustion chamber C sufiiciently high that it will maintain combustion ofthe pulverized-coal'without the aid of the gas. Should there be no response by the thermostatic stack controlled mechanism to the starting of the motor H-as, for example, when there was a failure of combustion in the furnace or an improper combustion in the fur- -nace-it is evident that the switch IOI would never be closed and thus relay coil I02 would not be energized to perform the above described functions. Under these circumstances, the contacts of mercury switch 10 would not be opened and the heating of the bi-metallic thermal element I5 would not be discontinued in the manner above described. Said thermal element T5 would, therefore, continue its deflection with "a consequent clockwise rotation of the plate 8I about its pivot 96 until the snap mechanism comprising the downwardly extending arm -II5, comprising a pair of spaced plates connected at their lower ends by a roller mounted .on a pin M6, was operated to such a position that said roller passed over the center of the cam .I I1 on plate I13 and rotated said plate .I I3 in a counter-clockwise direction about its pivot II I. Under these conditions, the switches I0 and "I9 carried on the plate I I3 would be moved to open circuit position. The condition of said plate II3 when thus moved is generally as illustrated in Fig. 12 though other parts thereof are different as said Fig. 12 illustrates another condition. It may be pointed out that said plate II3 carries a latch II8 which 00- operates with an adjustable stop I I9 whereby the time interval within which said plate II3 will be pivoted as above described in the absence of the operation of the coil I02 may be adjustably determined.

With mercury switch I thus moved to an open position, the current which is supplied to the thermal element I will be out off and said element will tend to restore to its normal position. However, as the lever I04 is in its lowered position, the point I I9 of the arm I06 thereof will drop into the notch I20 of plate 8| and prevent said plate 8I from rotating in a counter-clockwise direction to its normal position. (See Fig. 10.) Under these conditions, the gas switch I6 and the motor switch 11 will be locked with their contacts in an open position, the switches I0 and I9 will be locked with their contacts open and it will be impossible for the mechanism to return to the normal position until it is manually re-set. Manual re-setting of the mechanism is provided by thumb tab IZI on the lever I04 which may be reached from the outside of the covering for the control mechanism. By pushing upwardly on said thumb tab I2I, arm I06 will release the plate BI and allow it to return to normal, whereupon the snap action mechanism, including arm II5, will return the plate H3 to its normal position and close the contacts of switches I0 and I9. This safety device therefore requires a manual resetting of the mechanism where improper combustion takes place and serves as a warning to the operator that inspection of the system is desirable.

Another feature of the control mechanism res des in the provision for re-cycling thereof should there be a current interruption during the ignition period--that is, where there is a current interruption when the igniter I4 is energized and the thermal element 15 is deflecting and just before the gas switch I6 and the motor switch 11 are moved to a closed position. When the current in the floating primary winding 68 thus ceases to flow, the said winding 68 will drop and pivot the lever 81 to movethe pin 94 in a clockwise direction. Pin 94 will engage the arm 93 and will maintain the switches I6 and 11 in an open circuit position. As the lever 81 pivots, its carries with it the pivoted plate I22 which carries a pin E23 which, as best seen in Fig. 12, rides on a cam surface ofthe arm I06 to move said arm I06 in a counter-clockwise direction;- Arm I06 carries at its'top a pin I24 which, in normal operation, supports a plate I25 pivoted about a pivot I26. When the arm I06 is moved in a counter-clockwise direction as aforesaid, the pivoted plate I25 drops down'behind the pin I24 to prevent rotation of the arm I06 in a clockwise direction and thereby prevents the point II9 of the arm I06 from dropping into the notch I20 which, if allowed to take place, would require a manual resetting of the control device. This condition is illustrated in Fig. 12 of. the drawings. Further movement of the lever 81 under the influence of the downwardly moving floating primary winding to the dotted line position, illustrated in Fig. 12, carries the plate I22 until the bottom thereof contacts with the pin II2. This rotates the plate I iii upon which are mounted the switches I9 and 00 to open the contacts thereof. The cam III of said plate I I3 rides over the roller carried on pin litand is therefore held in position with said plate 8 l3 latched up as illustrated in Fig. 12. The circuit to the thermal element I5 is thus maintained open for the switch I is in open circuit position, and the thermal element I5 restores to normal. As said thermal element I5 restores to normal, the plate BI is rotated counter-clockwise and the arm i I5 strikes a pin I2I' carried on the plate 525 lifting said plate I25 about its pivot I26 and allowing the pin I24 to move beneath said plate I25, whereupon the arm I06 will assume its normal non-operative position. In addition, the roller carried on pin I I6 will snap over the cam III of plate H3 and thereby move the switches I0 and I9 to their normally closed position as the thermal element I5 reaches its normal position. The control mechanism is therefore completely re-set by automatic operation and is ready to start another cycle of operation without requiring any manual re-setting thereof. It is, of course, desirable that said control mechanism be required to re-cycle upon a current interruption for otherwise a short current interruption might be sufficient to cool the incandescent ignition means It so that, were the gas and pulverized fuel fed to the furnace, there would be a failure of combustion due to the lack of proper incandescence of said. ignition means I4.

Means are also provided for completely shutting down the system and automatically starting it up again in a normal manner Should there be a current interruption during the running condition of the system; that is, when the motor H was operating to deliver pulverized coal to the furnace under the control of the room thermostat 66, as was above mentioned. Should the current fail during a running condition, it is extremelydesirable that the apparatus automatically shut down and then start again for otherwise upon a short interruption of current the primary combustion chamber might become so cool that it would not support combustion, yet the stack operated switches 80 and IOI might still be closed due to the stack temperature. Unless properly cared for, such a condition might be very dangerous.

The normal running condition of the control apparatus is illustrated in Fig. 11. Upon a current interruption, the dropping of the floating primary winding 60 would cause the pin 94, carried on lever 81, to lock the gas switch I6 and the motor switch 11 in an open position. Armature I03 will be released and switches I0 and I9 will be moved to their normally closed position. Let us assume that the stack temperature has fallen insufficiently to open the contacts of switch I01 and the contacts of room temperature responsive switch 66 are closed when the current is restored. Under these conditions, relay coil I02 will be en rgized the moment the current is restored. This will move the armature I03 which will, in turn, rotate the arm I06 in a counterclockwise direction so that the top of said arm I06 will engage beneath the tongue of the carrier plate M. This will effectively lock the carrier plate 9! in a position with the contacts of the gas switch I6 and the motor switch 11 open. Under these conditions, neither gas nor pulverized coal can be supplied to the furnace and the condition will persist until the stack switch IOI has opened, whereupon relay coil I92. will be deenergized and the entire mechanism restored to its normal non-operating position. Thereupon, the said control mechanism will be in a condition to start a new period of operation, if room temperature responsive switch 66 is still closed.

lit is thus evident that with the control circuit of Fig. 3 and with the control mechanism of Figs. 9, 10, 11. and 12 a very flexible and very efficient system of automatic control is provided.

The incandescent ignition means #4 is energized for a predetermined period as a first incident to starting up of the furnace. After it is heated to incandescence, gas and pulverized fuel are supplied to the furnace to initiate combustion,

the gas being turned on for a very short interval prior to the time the pulverized coal is fed to said furnace. Thereafter, in response to normal combustion conditions, the ignition means 14 is disabled while the gas is supplied for an additional period. The system is so adjusted that the gas supply is continued until the temperature in the preliminary combustion chamber is sufficient to maintain the combustion of the pulverized coal without the aid of gas. This period is generally sufficient to heat the walls of said preliminary combustion chamber C to approximately 2000 to 2500 degrees Fahrenheit. After this preliminary combustion chamber temperature is reached, the gas is automatically shut off and the pulverized fuel is supplied under the direct control of room temperature responsive thermostat 66. Thus the temperature in the room in which thermostat 66 is placed may be automatically controlled. It is evident that the switch 66 may be controlled by either room air temperature or by water temperature where a hot water system is used or by a combination of the two where said hot water system is employed.

Referring particularly to Fig. 4 of the drawings, there is illustrated another embodiment of my invention which employs the control apparatus of Figs. 9, 10, 11 and 12. This circuit is in general very similar to the circuit of Fig. 3 and attention will be first directed to the features in which they differ. In Fig. 3, there is an individual gas switch 16 and an individual motor switch TI, both of which are mounted on the carrier plate 9|. In the system of Fig. 4, a combined gas and motor switch 1'! is employed instead of the two switches 16 and 11. This will, of course, mean that the gas valve Zia and the motor H in the system of Fig. 4 will be turned on together in the normal operation of the device. In addition, in the system of Fig. 3 a single stack temperature responsive device was employed to operate switches I III and 80 though they were operated at different speeds. Such an arrangement may also be employed to operate the switches ID! and 80' in the system of Fig. 4, but I prefer to employ separate thermostatic stack controlled mechanisms IOUa and 19Gb in the system of said Fig. 4. That is, a relatively fast stack controlled mechanism I001) will be employed for operating the switch NH and a relatively slow stack controlled mechanism IOOa will be employed for operating the switch 80'. With these differences in mind, the operation of the system of Fig. 4 will be obvious.

Briefly described by using primed reference characters to denote elements in Fig. 4 similar to the same elements in Fig. 3, the normal operaticn thereof will be as follows:

Upon the closing of the room temperature responsive switch 66' in response to a pre-determined low room temperature, the circuit to the secondary 55' of the transformer 63' will be closed and the normally open contacts of mercury switch 61 will be closed. It is evident, of course, that the primary winding 64 of the transformer 63 is supplied with current from the line conductors 60' and GI in the latter of which there may be provided a safety switch 62 operated by an excessive pressure or excessive temperature controlling device. Upon the closing of the contacts of said switch 61, the

floating primary 68 of constant current transformer 69 will be energized through the normally closed contacts of the mercury switch 16.

Current will therefore flow in the series circuit including the secondary 13 of the transformer 69', the incandescent ignition means 14 and the bi-metallic terminal element 75'. This will result in the lifting of the floating primary winding 68 and the deflection of the thermal element 15', as was above described in connection with the system of Fig. 3. Thermal element 15' upon deflecting a pre-determined amount will close the normally open terminals of the combined gas and motor switch 11 after a predetermined adjustable time interval during which the ignition means 74' has reached incandescence. On the closing of the contacts of switch 11', the gas valve solenoid 18' will be energized through the contacts of normally closed switches 19 or .80 in parallel, and the motor H which operates the feed mechanism G will start into operation to feed pulverized coal to the furnace. Solenoid 18 will, of course, operate the gas valve I Zia to supply gas to the furnace which will be ignited by the ignition means 74' and which ignited gas will ignite the pulverized coal. Combustion will therefore be initiated.

In the system of Fig. 4, it is thus to be noted that the gas valve Na and the motor H are first energized simultaneously while in the system of Fig. 3 the gas valve 2la is open a very short interval before the motor H is started. The system of Fig. 3 therefore has an advantage over that of Fig. 4 in that ignition of the gas ordinarily takes place before the pulverized fuel is supplied to the furnace. However, the system of Fig. 4 is more simple in that a single mercury switch 71' performs the function performed by the two mercury switches 16 and 11 in the system of Fig. 3.

After combustion is initiated, the fast operating stack controlled mechanism I001) will close the contacts of the normally open mercury switch ID! in response to' combustion temperature for a short period. This opens the contacts of normally closed mercury switches and 19. The former de-energizes the floating primary winding 68 and allows it to drop with the consequent deenergization of the ignition means 14' and the thermal element Thermal element I5 therefore starts returning to its normal de-energized position. The gas valve 2|a is maintained open for a longer period for, though the contacts of mercury switch 19' are open, the circuit to the solenoid 18' is maintained closed through the closed contacts of mercury switches 80 and 71. Thus the gas is maintained on with the pulverized coal after the ignition means 14' is shut off and until the preliminary combustion chamber C has had an opportunity to reach a sufficiently high temperature to maintain the combustion of the pulverized coal without the aid of the gas.

After a pre-determined period of combustion, which may be adjusted by operation of the stack temperature responsive device IOUa, the contacts of mercury switch 80' are moved to an open position whereupon solenoid I8 is de-energized and the gas valve 21a is closed, resulting in the shutting down of the gas supply. The operation of the motor H is thereafter under the direct contIOl of the room temperature responsive switch 6 All of the safety features which were described in connection with the system of Fig. 3 fully apply to the system of Fig. 4 and thus need not be repeated. It is thus evident that the control system of Fig. 4 has substantially all the capabilities of operation of the control system of Fig. 3 which were above set forth except for such distinctions as were specifically mentioned. It is therefore. to be understood that the description of the system of Fig. 3 applies with equal force to the system of Fig. 4 except for such differences as are specifically pointed out above.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I wish therefore not to be restricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of my invention, what I desire to secure by Letters Patent of the United States is:

1. In a system for burning fluent fuel, the combination with a furnace including a main combustion chamber, of a preliminary combustion chamber within said main combustion chamber, a fluent fuel delivering means including a motor, an electro-magnetic gas valve, ignition means, parallel circuits for said motor, valve and ignition means, a thermostatically controlled switch for closing and opening all of said circuits, a switch individual to said electro-magnetic gas valve, a switch individual to said ignition means, a shunt circuit for said gas valve switch including a combustion temperature controlled switch, and initial temperature responsive means adapted to open the switches individual to said gas valve and ignition means responsive to initial combustion, said shunt circuit combustion temperature controlled switch being effective to maintain said gas valve open for a period after said initial temperature responsive means opens said individual switches and until said preliminary combustion chamber reaches a fluent fuel combustion supporting temperature.

2. In a system for burning a fluent fuel, the combination with a fuel motor and a motor circuit, ignition means and an ignition circuit, and a gas valve and a gas valve circuit, of a thermally controlled switch for energizing all of said circuits in response to a predetermined low temperature, combustion responsive switches for disabling said gas valve and said ignition circuits respectively, said switches being adapted to open said circuits in response to initial combustion, and a shunt circuit for said gas valve switch including a second combustion temperature responsive switch, said second combustion responsive switch opening after said first mentioned combustion temperature responsive switches are operated whereby said gas valve will be operated for a prolonged period beyond the period of energization of said ignition means.

3. In a system for burning a fluent fuel, the combination with a fuel motor, an electro-magnetic gas valve, and ignition means, of parallel circuits for said motor, valve and ignition means, a thermostatically controlled switch for closing and opening all of said circuits, a switch individual to said electro-magnetic gas valve and a switch individual to said ignition means, a shunt circuit for said gas valve switch including a combustion temperature controlled switch, initial combustion responsive means adapted to open the switches individual to said gas valve and ignition means responsive to initial combustion, said shunt circuit combustion temperature controlled switch being effective to maintain said gas valve open for a prolonged period and after said ignition means is rendered inoperative until a high combustion temperature is reached.

4. In a system for burning a fluent fuel, the combination with a fuel motor, an electro-magnetic gas valve, ignition means, of branch circuits individual to each of said elements, a line common to all of said branch circuits, a thermostatically controlled switch in said line, a first switch in the branch circuit including said gas valve, a second switch in the branch circuit including said ignition means, initial combustion responsive means for operating said first and second switches, a shunt circuit for said first switch including a third switch, prolonged combustion responsive means for operating said third switch whereby said gas valve will be maintained open for a prolonged period, and means for discontinuing operation of said system to require manual re-setting thereof when combustion does not begin within a predetermined time after said thermostatically controlled switch is operated.

EARLE V. FRANCIS. 

